As investigated by Nicolas on #kde-devel, the "dolphin.git" repository has a bad push of a master commit to Applications/17.12 branch.
The offending commit is 9a7569a82a29b00b0373892603791be1ab879e4d from 2018-02-14.
Since this blocks the KDE Applications 17.12.3 tagging on Monday, this needs to be resolved as soon as possible. Unfortunately, I did not check the state before committing the version update.
Please coordinate with Nicolas; he may already have taken actions.